FA-60705 / Loyalty points ledgers / Member archive

Birthday bonus window: neighbouring birthday years · case 05

Purchases in late December miss an early-January birthday window.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Input {bmonth, bday, window, bonus, purchases:[[y,m,d]] chronological}. The birthday of year Y is (Y,bmonth,bday), with Feb 29 falling back to Feb 28 in non-leap years (Gregorian rule). A purchase within window days (inclusive, either side) of the birthday of year Y-1, Y or Y+1 earns the bonus once per birthday year. Return per-purchase bonus list.

Why this case matters

Member point balances, statements and the program liability depend on this ledger rule.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
year crossing	`[0, 300]`	`[300, 0]`	Failed

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